Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Touch sensor panels are typically fabricated by depositing and patterning conductive material into a set of conductive elements upon one or more sides of a transparent substrate. The number of sides used in a particular architecture can depend on a variety of factors; however, in many instances, single-sided touch sensor panels are preferred since they are both cheaper to manufacture and require less space.
On a single-sided touch sensor panel, however, conductive routes must share the same side of the substrate. In many cases, this can result in parasitic capacitive coupling as conductive routing used for drive lines runs alongside sense lines on the touch surface. Moreover, when a touch event occurs in a particular region of the touch surface, the touch event can alter the parasitic capacitive coupling and produce spurious signals that can erroneously appear to be touch events in untouched regions of the touch surface.